The head of the State Police said he has disbanded the agency’s decades-old drug diversion unit and auto theft strike force to deal with current realities: a shortage of troopers, a budget shortfall, and increased responsibilities.

Colonel Timothy P. Alben said the dissolution of the two squads at the end of December allowed him to shift 25 troopers to the Massachusetts Turnpike and Logan International Airport, both areas where police vacancies have gone unfilled and more forces were needed. He said it will also help him reduce a $3 million deficit in this year’s State Police budget because their salaries will come from the highway and airport budgets.

“We are trying to show we are being diligent with taxpayer dollars and putting resources toward issues most important to people of Massachusetts,” Alben said in a phone interview Thursday. “We are at the mercy of the economy.”

But the dissolution of the eight-member drug diversion unit, which was created in 1974 to target the theft and illegal distribution of prescription drugs, drew sharp criticism from a South Boston legislator who called the rampant abuse of OxyContin, heroin, and other drugs one of the biggest issues facing the state.

“I’m disappointed to hear the State Police are disbanding this unit, it suggests that their priority isn’t there anymore,’’ said Representative Nick Collins, a Democrat. “We’re looking at a situation not just in my community, but across Massachusetts, that is epidemic. More and more deaths happen every year and shouldn’t. . . . To me this is the number-one public safety challenge that we’re facing in the Commonwealth.”

Alben said the State Police are not abandoning the types of investigations handled by the drug diversion unit; those cases will be handled by State Police narcotics units assigned to the district attorneys. Legislation passed last year cracking down on prescription drug abuse will probably lead to more investigations by local police, he said.

The law requires drug manufacturers, dispensers, and distributors — including doctors and pharmacists — to report the loss or theft of controlled substances to local police, where previously, only State Police and the federal Drug Enforcement Administration were notified.

‘We are at the mercy of the econ-omy.’

Collins, one of the staunchest supporters of the legislation, said the goal was to focus more law enforcement attention on prescription drug abuse.

“Though federal and local law enforcement agencies play a significant role, we need a full team effort to fight this battle and by disbanding their drug diversion unit, the State Police seem to not want to be on the team,” he said.

Alben said that in addition to this fiscal year’s $3 million deficit, State Police are facing a dwindling workforce and increased responsibilities. He moved 17 troopers to the Massachusetts Turnpike and eight to Logan International Airport. He said the troopers are moving into jobs that had remained unfilled after retirements. Their salaries are paid by the Department of Transportation and the Massachusetts Port Authority.

Alben, who was sworn in as head of the State Police last July, said the department has lost about 500 troopers through attrition since 2006 and is desperate to replenish its ranks, currently at 2,187 troopers. A new class of 150 recruits is set to report in June, but Alben said the department needs $10 million to get them through training.

More troopers are especially important now, Alben said, because State Police have been given the added responsibility of providing security for casinos.

“This comes to a point where this really starts hurting public safety, and I think we are at that point now,” said Alben, referring to the need for more troopers.

He lauded the work of the drug unit and the auto theft strike force, but said he plans to focus more on violent crime, gangs, cracking down on drunk drivers, and homeland security.

The 17-member auto theft strike force made 328 arrests in 2011 and recovered vehicles valued at $9.67 million. The squad was created by Governor Michael Dukakis in 1983 when the state was dubbed the stolen car capital of the nation by officials who said that the previous year, more cars were stolen in Massachusetts per 100,000 residents than in any other state.

Though California has consistently led the nation in total cars stolen, Massachusetts ranked third from 1971 to 1976, peaking at 91,563 in 1975, according to the FBI’s Uniform Crime Reporting Statistics.

In 2011, the latest year that statistics were available, Massachusetts was ranked the 21st state in the nation, with 10,786 cars stolen.

Frank Scafidi, a spokesman for the National Insurance Crime Bureau headquartered in Illinois, said car theft rates have dropped dramatically in recent years with new antitheft and tracking technology, and police departments around the country have disbanded specialized auto theft units to devote more resources to other crimes.

“It doesn’t mean it’s not still a problem in some areas,” Scafidi said. “But if you’re a police department in LA and have gangs, burglaries, drive-by shootings, and no-victim auto theft cases, you can almost guess where that is going to fall on their list of things to do.”

Despite the successes, according to the National Highway Traffic Safety Administration, a car is stolen in the United States every 33 seconds and only 57 percent of those reported stolen are recovered.

The disbanding of Massachusetts’ auto theft strike force also marks the end of a state-operated hot line that the public called to leave the State Police confidential tips about stolen cars. Alben said the public should call 911 or their local police with tips.

Scafidi said the National Insurance Crime Bureau operates a nationwide hot line and urges people to call anonymously with tips on insurance fraud, vehicle theft, and chop shops. The tips called into the number, 800-TEL-NICB, are monitored by the nonprofit agency and referred to local police.

“I would be surprised if there’s not some kind of follow-up regardless of how many specialized units exist or don’t exist,” Scafidi said. “Crime is crime and cops at the end of the day like to put bad guys in jail.”